Ethernet switching technology provides high bandwidth, low latency, and scalability for large datacenters and computers for data communication. A number of approaches have been used to exploit multiple paths in an Ethernet. For example, the network can be partitioned using layer-three Internet Protocol (IP) subnets or layer-two Virtual Local Area Networks (VLANs). Although these approaches limit the scope of flat layer two networks and assist in exploiting multiple paths, complex and costly manual administration are still required.
Another protocol developed to enhance Ethernet networks is hash-based routing based on fat trees. Fat trees are constructed in tiers to allow switches of fixed radix to scale to networks of arbitrary size and bisection bandwidth. When a message flows from a source to a destination, a sequence of multiple uplink choices are confronted until a root switch is reached. These techniques provide load balancing for multipath networks while preserving the simple administration of plug and play networks, which results from the learning functions of transparent bridging. However, a critical problem for hash-based routing occurs when one or more links or switches fail, which disrupts normal network communications. Unlike a regular tree, which includes only a single top switch, the fat-tree structure includes a larger number of uplinks and top switches. Therefore, the probability of failure in the fat-tree structure is increased.